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The issues is not wiring in a way to keep the thermostat powered up, it's getting the furnace situation corrected since it's not operating properly. We don't want to "hide the problem" by wiring in a control circuit. It makes me wonder how many systems out there with battery powered thermostats are hitting the limit and the customer doesn't even realize it.

My guess is, if the furnace it not working, that is would prompt most home owners to call for service, regardless.

Originally Posted by 54regcab

It makes me wonder how many systems out there with battery powered thermostats are hitting the limit and the customer doesn't even realize it.

You totally lost me here.

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“Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

Furnaces can still "work" even though they are shutting off on high limit. They run for a few minutes, go off on limit while the blower continues to run and blow hot air into the house. Once the furnace cools it resets and runs again. As long as it's not being used near capacity a homeowner may not notice this behavior, especially if the blower doesn't completely cycle off each time.

Pre-90's furnaces like you were talking about earlier that just cut the voltage from the gas valve while keeping the blower running would just keep working as far as he homeowner knew, unless they were hearing/watching the burners cycle.

Pre-90's furnaces like you were talking about earlier that just cut the voltage from the gas valve while keeping the blower running would just keep working as far as he homeowner knew, unless they were hearing/watching the burners cycle.

You really need to stop posting and do a little research before you post. The old style furnaces would not keep running, when the stat was satisfied, it would kill the power to the gas valve, and then the fan limit would cool, and shut off the blower motor.

__________________________________________________ _______________________
“Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

You really need to stop posting and do a little research before you post. The old style furnaces would not keep running, when the stat was satisfied, it would kill the power to the gas valve, and then the fan limit would cool, and shut off the blower motor.

I meant on the high limit switch not thermostat. When the old furnaces hit limit what is supposed to happen?

Would this setup work well with this much sq. ft. International Falls, Minnesota?

Also, for any house that size that requires that little heat, just how much cooling is required. If that house is in an area far enough south to not need the least amount of heat that is available in a gas furnace, then a heat pump system would be the way to go, like is done in other Southern areas.

Since reg is refusing to give us specifics about the applications he is claiming, we have nothing to go on in order to find out why he has so many more issues than anyone else in the country.

Cutting the power to the thermostat means no power to the W terminal from the thermostat. The furnace may very well have an additional safety on the W terminal.

The power is not cut to the thermostat when a high limit switch opens. I've never seen a furnace that cuts the power to the thermostat when a high limit circuit has opened. Follow the power from the transformer in order to understand what that circuit is doing.

Furnaces can still "work" even though they are shutting off on high limit. They run for a few minutes, go off on limit while the blower continues to run and blow hot air into the house. Once the furnace cools it resets and runs again. As long as it's not being used near capacity a homeowner may not notice this behavior, especially if the blower doesn't completely cycle off each time.

Pre-90's furnaces like you were talking about earlier that just cut the voltage from the gas valve while keeping the blower running would just keep working as far as he homeowner knew, unless they were hearing/watching the burners cycle.

This is all indicative of an improperly sized duct system, air blockage such as dirty filter or coil, loss of blower capacity etc. None of this has anything to do with the furnace being oversized.

What is the point of all of this rambling of yours? What are you trying to get at?

You really need to stop posting and do a little research before you post. The old style furnaces would not keep running, when the stat was satisfied, it would kill the power to the gas valve, and then the fan limit would cool, and shut off the blower motor.

Exactly. On older furnaces, the blowers were energized strictly by temperature. I've seen furnaces in attics turn on the blower because of heat build up during the hot Summer days.

You know it's one thing to want to learn the trade, and just humble yourself and sit back and watch and listen, but when your argument is not fact, and you don't just stop for a moment to research something before you post, you not going to appear to be the brightest bulb in the house. It's like me going on a TV repair forum and and telling all the pro's there how a TV works or is wired.

__________________________________________________ _______________________
“Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law